24 Pa. Stat. § 10-1079
Whenever a board of school directors finds it impossible or impracticable to fill immediately any vacancy occurring in the position of district superintendent or assistant district superintendent, the board may appoint an acting district superintendent or an acting assistant district superintendent to serve not longer than one year from the time of his appointment.
When a leave of absence has been granted to any district superintendent or assistant district superintendent, and it is deemed necessary or desirable, the board of school directors may appoint a substitute district superintendent or assistant district superintendent to serve for such period of time as the regular district superintendent or assistant district superintendent is absent on leave.
24 P.S. § 10-1079